1. Field of the Invention
The present invention relates to a ureteral stent placed between a kidney and a bladder.
2. Description of the Related Art
A process for placing a ureteral stent in a ureter in order to protect the ureter from being narrow and reserve a flow path of urine. The ureteral stent has been requested for reducing the burden on a patient and reserving the flow path of the urine.
When a calculus appears in the kidney or ureter, a process is often performed for using ESWL (Extracorporeal Shock-Wave Litotripsy), and chopping the calculus and then discharging the chopped calculus pieces through the ureter from a body. After the calculus is chopped, the ureteral stent is placed to reserve the urine path.
Japanese Laid-Open Patent Application (JP-A-Heisei, 6-238007) discloses a ureteral stent characterized by having a lead portion, a main body and a tail portion and having a lumen therein, wherein the main body is at least constituted by a super-elastic metal tube and an outer diameter (φ0) and an inner diameter (φi) of the super-elastic metal tube are defined so as to satisfy the following equations (1) and (2).φ0≦3000 μm  (1)200 μm≦(φ0−φi)/2≦150 μm  (2)
PCT application WO/2002/053065 discloses a radially expanding ureteral device. The ureteral device is provided for facilitating stone passage through a ureter or duct. An exemplary ureteral device includes a flexible, elongate body that defines a plurality of cages along the body. In a contracted state the cages have a reduced diameter. When an activation force is applied, the cages transform to an expanded state, thereby defining a plurality of void spaces. The void spaces are configured to receive an obstruction, such as a stone.
Japanese Laid-Open Patent Application (JP-P2003-19211) discloses a stent. The stent is disintegrated in a living body after staying in the body for a time appropriate for a therapeutic purpose.
Japanese Patent (JP2888979-B2) discloses a stent for removing calculus and its fragments. The stent includes an elongate and flexible tube.